Before the Internet there was the ARPAnet, the first distributed computer network, launched in 1969.
Following is some background on the role Doug Engelbart and his SRI lab played in the early formation of the ARPAnet, and the vast potential he envisioned for its continued evolution.

Since the early 1950s, Doug had envisioned people working together on complex, urgent problems in a vast information space via interactive computers. By the early 1960s, at Stanford Research Institute (now SRI International), he had launched a research center for "augmenting the human intellect" in support of collaborative problem solving. Throughout the 1960s and '70s he and his team pioneered an interactive computer system called NLS which integrated collaborative hypermedia with the mouse and rudimentary GUI, onscreen authoring, shared documents, digital libraries, computer-supported meetings, teleconferencing, and more. You can see most of these features demonstrated in his 1968 "Mother of All Demos." NLS was used extensively by his team in all aspects of their work, and now they were looking forward to making it available over a distributed network.

At the same time, Doug's research was sponsored primarily by Bob Taylor[1] at the US Defense Advanced Research Projects Agency (ARPA).
In the mid 1960s, Taylor conceived an initiative to network the computer labs he was funding at ARPA to make it easier to access and share their research and computer resources. In 1967 he enlisted four of those labs to help implement this network, which was being developed at Bolt, Beranek, and Newman (BBN). Engelbart was thrilled with the concept, which dovetailed beautifully into his vision, and he was one of the first PIs to volunteer. UCLA, Utah, and UC Santa Barbara were also on board. Representatives from the four sites, including Doug's chief software architect Jeff Rulifson, began hashing out the details. From their early meetings under UCLA Steve Crocker's direction the Network Working Group and the concept of the RFCs quickly emerged. Watch as Doug unveils plans for the ARPAnet in his Mother of All Demos [clips 32 & 33].

The ARPAnet went live in 1969. The first two sites to come online were Kleinrock's lab at UCLA, and Engelbart's Augmentation Research Center at SRI.

When it came time to test transmission over the network between the two sites, the task fell to two young programmers -- Bill Duvall in Doug's lab in Menlo Park, CA, and Charlie Kline in Len Kleinrock's lab at UCLA, in Los Angeles, CA.

"On October 29, 1969, the world's first electronic computer network, the ARPANET, was established between nodes at Leonard Kleinrock's lab at UCLA and Engelbart's lab at SRI. Interface Message Processors at both sites served as the backbone of this first [network]"[2]. The first message sent between them was to be "log" from UCLA to SRI, and "in" from SRI to UCLA ("login") but the computer crashed after the first two letters so the first message between computers was simply "lo". (see [2] for more on this story).

The UCLA team were also tasked with running a Network Measurement Center for the ARPAnet to monitor network performance, while Engelbart's team was tasked with running a Network Information Center to support the ARPAnet community with information about the network and host resources available on the network.
Doug's lab set to work extending NLS provisions for community support[3], including integrated hyper-email and an automated online publishing facility (the "Journal"). By 1978 there were 5-6 mainframes running NLS over the ARPAnet, as well as over several commercial networks (Tymnet and Telenet), supporting dozens of user organizations and their networks. The NIC ran on a version of NLS.

In 1974 Elizabeth "Jake" Feinler joined Doug's group to oversee the NIC, working closely with Jon Postel, Steve Crocker, and others. The NIC soon took on a life of it's own as a spinoff, with Jake as Principal Investigator.

This map shows the entire ARPAnet in 1969 with the first four nodes, including Engelbart's lab at SRI. Click the map to see full size at the source site which maps its growth over time.

By 1972 there were 37 nodes on the ARPANET. Soon other networks spang up, such as the commercially-available Telenet and Tymnet, each operating in isolation of the other, for there were as yet no provisions for communicating between these networks. The Internet later emerged as an architecture for internetworking, extending this single-network design to any number of networks, which would allow every host in a network to communicate with every host on every other network that became a part of the system.

Following are references to the passages from Engelbart's
papers in the late '60s and early '70s which highlight his
lab's orientation for Network Implications prior to and during
the formation of the ARPAnet, all directly related to today's
Internet and World Wide Web as well.

1962:Doug "backcasts" a picture of networked professionals
"Let me mention another bonus feature that wasn't easily fore seen. We have experimented with having several people work together from working stations that can provide inter-communication via their computer or computers. That is, each person is equipped as I am here, with free access to the common working structures. There proves to be a really phenomenal boost in group effectiveness over any previous form of cooperation we have experienced. [â¦] The whole team can join forces at a moment's notice to 'pull together' on some stubborn little problem, or to make a group decision."
– Augmenting Human Intellect: A Conceptual Framework, Douglas C. Engelbart. SRI Report, 1962. See especially what he envisioned for accessing the computers remotely via 'workingstations' in this 'backcast' on Team Collaboration.

1970: Doug writes about the implications of networking
"there will emerge a new 'marketplace,' representing fantastic wealth in commodities of knowledge, service, information, processing, storage, etc. In the number and range of transactions, and in the speed and flexibility with which they are negotiated, this new market will have a vitality and dynamism as much greater than today's as today's is greater than the village market."
– From Doug's paper given at a small conference organized by Larry Roberts, Bob Taylor's Program Manager for the ARPAnet initiative. Each invited speaker was to address his relevant "Implications of Multi-Access Computer Networks." For instance, Larry's was "Economic Implications." Engelbart's was "Intellectual Implications": Intellectual Implications of Multi-Access Computer Networks, Douglas C. Engelbart, Stanford Research Institute, 1970 (AUGMENT,5255,). From Proceedings of The Interdisciplinary Conference on Multi-Access Computer Networks, Austin, Texas, April 1970.

Fast forward to the early 1990s when Doug reemerged with a Call to Action on the order of a Grand Challenge to spur proactive industry-government exploration into what it will take to boost our collective intelligence in business and society to the fullest extent possible. He proposed spinning up a number of specially-endowed pilot teams leveraging the most advanced modes of working together, enabled by highly evolved information technology and processes. To speed things along he detailed what he saw to be the baseline requirements for the technology, which he called "open hyper document systems" and which he pointed out as a serious matter were largely missing from then prevailing IT paradigm. It is important to note that most of these requirements are still largely unmet in any coherent way in today's IT paradigm, his Grand Challenge as yet unheeded (now referred to as "Engelbart's Unfinished Revolution" in contrast to the revolution(s) inspired by his work that did take hold).

“
Some of the most creative minds in our field were gathered in Doug's laboratory to explore the augmentation of human intellect through the use of computers. [â¦] NLS was a prototype for what came 20 years later in the form of the World Wide Web although it may be fair to say that Doug's vision and even the functionality of NLS exceeded in some ways what has been accomplished with the Web.
”
– Vint Cerf The 'Father of the Internet' Remembers Douglas Engelbart, July 2013

For his visionary work related to networking and the foundations of the information age, Doug Engelbart was inducted into the Internet Hall of Fame, and received the National Medal of Technology and Innovation, the Webby Lifetime Achievement Award, the SoftQuad Web Award, the IEEE John Von Neumann Medal Award, the Benjamin Franklin Medal, ACM's A.M. Turing Award, and the American Ingenuity Award.
See Honors Awarded to Doug Engelbart for details and a complete listing.

"The Mother of All Demos" (90 min Video/Film) Doug's 1968 debut of NLS (Augment's precursor) including hypermedia, the mouse, collaborative work, interactive computing, human computer interface, and overarching guiding principles. See especially Clip 32 and Clip 33 where Doug outlines the participation of ARC in the planned ARPA computer network to be established within the next year (1969).

Their 1968 paper published in the FJCC Conference Proceedings has been somewhat masked by the publicity given to the online presentation they gave at the Conference (aka the "Mother of All Demos"), but it outlined in detail the hardware, software and functionality of the NLS system: A Research Center for Augmenting Human Intellect, Douglas C. Engelbart and William K. English, AFIPS Conference Proceedings of the 1968 Fall Joint Computer Conference, San Francisco, CA, December 1968, Vol. 33, pp. 395-410.

ARPA stands for Advanced Research Projects Agency, now DARPA or Defense
Advanced Research Projects Agency, a funding agency of the US
Department of Defense which was the major source of R&D
funds for early computer and network research.
For Bob Taylor's rendition of events, see his one on one discussion with John Markoff at the Engelbart and the Dawn of Interactive Computing event.